Pump noise vs pressure

Transmission to Rear-end

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Circlotron
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Pump noise vs pressure

Post by Circlotron » Thu Jan 14, 2016 7:34 pm

My car has a TH700R with a Corvette servo and some kind of shift kit. Was already fitted when I got the car. Between approx 1300-2000 rpm there is a slight whirring or groaning sound that spoils the otherwise smoothness of the car. Nothing alarming though and nothing has changed in the last five years so it's not about to quit or anything. I am wondering could the front pump be making this kind of sound because of higher than stock pressure? It definitely varies in pitch with the input side of the tranny.

Greenlight
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Re: Pump noise vs pressure

Post by Greenlight » Sat Jan 16, 2016 2:54 am

There is a known problem in that transmission with the pressure regulator valve on some year model transmissions.

GM issued a Technical Service Bulletin # 277142, which discussed the pressure regulator valve oscillating due to pressure instability. The fix was to replace the pressure regulator valve with an improved design (Part # 8684048). I'm not sure if that is still a good part number. I think the pressure regulator valve can be replaced with the pan removed, but I'm not completely sure.


Please make sure the Throttle Valve (TV) cable is adjusted properly.
Project Greenlight

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